Chapter 23. Code coverage

Erlang.mk provides support for code coverage via the tool
cover that comes with Erlang/OTP. Code coverage lets you
see what parts of your code are covered by the tests.

23.1. Enabling cover when running tests

To run tests with code coverage enabled, simply define
COVER=1 either on the command line or in your Makefile:

$ make tests COVER=1

When running the targets tests or check the code
coverage report will be built automatically. This is
not the case for test framework specific targets,
however. In those cases you can generate the reports
manually:

$ make eunit proper COVER=1
$ make cover-report

Note that Common Test has some support for cover
built-in and that it will generate code coverage
reports in the Common Test logs regardless. The
report that Erlang.mk generates is however common
to all test frameworks and might be more useful.

23.2. Adding applications to the cover report

By default Erlang.mk will include all the applications
in the code coverage report, except external dependencies.

To include some dependencies in the report, you can
define the COVER_DEPS variable:

COVER_DEPS = cowlib

When using multi application repositories you can exclude
some applications by defining the COVER_APPS variable:

COVER_APPS = presence backend

23.3. Configuring paths

By default Erlang.mk will store coverdata files and
code coverage reports under the cover/ directory. The
variables COVER_DATA_DIR and COVER_REPORT_DIR can be
set to use a different location.

23.4. Merging coverdata files

The target all.coverdata will take all existing
coverdata files and merge them into one: